If only they'd go back and do character songs for the Black Moon arc and Season III (ending songs don't count as character image songs).
Ai Maeda, Pluto's vocalist, is well known for her songs in the Digimon anime (this one is my personal favorite) and it's a shame we can only hear a bit of her on Astral Mission and Moon Effect.
(Imagine if Crystal had her sing a brand new ending song for the Black Moon arc instead of having to make us suffer through Gekkou for another 12 episodes? )